This invention relates to systems for converting solar energy to electrical energy or mechanical energy. The invention has potential use by large electrical utility companies or private power plant owners. It could also be used by automotive vehicle service station companies to provide an alternative fuel to gasoline or diesel fuel.
The invention contemplates a large array of photovoltaic cells (solar cells) covering several acres of land to generate direct current. Some of the generated current is supplied to an electrolysis unit that converts liquid water into gaseous hydrogen and gaseous oxygen. Some of the generated current is sent to a cryogenic cooling unit that liquidifies the oxygen and hydrogen. The two separate liquids are pumped into separate tanks on transport vehicles (that can be either railroad cars or trailer-type road vehicles).
The use of transport vehicles for the liquid oxygen and liquid hydrogen is advantageous in that it enables the solar cells to be located in a rural area remote from the end use point. Acreage for the solar cells can be mountainous land or desert land that is relatively economical to acquire, but is nevertheless well suited to the attainment of high solar cell operation efficiencies (i.e. land that has predominately sunny cloudless days, and a high sun orbit). By using low cost land for the solar cells it should be possible to reduce the capital expenditure associated with the production of liquid oxygen and liquid hydrogen.
In one form of the invention, the transport vehicles deliver the liquid oxygen and liquid hydrogen to a geographical site that includes a steam boiler, steam turbine and turbine-driven electric generator. The liquid oxygen and liquid hydrogen are burned in the boiler to heat (produce) steam, which is circulated through the turbine. The turbine powers the electrical generator, which produces electricity as the end product.
A major advantage of the proposed system is the fact that liquid oxygen and liquid hydrogen can be produced from solar energy (using a suitable water supply) at one geographical site selected for the climate (exposure to solar energy) and low acquisition cost; whereas the boiler, turbine, and electric generator can be located at a second geographical site selected for other factors, e.g. a site in near proximity to electrical customers, and or a site already having the necessary boiler, turbine and electric generator. The purpose in liquefying the oxygen and hydrogen is to reduce the transport volume so that the oxygen and hydrogen can be economically transported from one geographical site to another site.
Prior to this invention, others have suggested various process steps used in the practice of my invention.
U.S. Pat. No. 3,459,953 which issued to W. L. Hughes, et al, discloses an electrical production system wherein an electrolysis unit 16 supplies gaseous hydrogen and gaseous oxygen to storage devices 20 and 22. The gases are burned in a burner 24 that produces steam for powering a steam tubrine 32. Mechanical power is thus delivered to an electric generator 36. Apparently, the entire system (apparatus) is located at one geographical site.
U.S. Pat. No. 4,161,657 discloses an apparatus that is powered by solar rays to produce an electric current. The current is applied to an electrolysis unit which converts liquid water into gaseous hydrogen and oxygen.
U.S. Pat. No. 4,227,374 which issued to A. Oxley shows an energy storage system that includes a Stirling refrigerator 19 driven by a steam turbine 12 to produce liquid oxygen. The oxygen is stored in a tank 21 which connects to a heat pipe 31 and Stirling engine 27.
U.S. Pat. No. 4,650,544 which issued to Roy Gordon relates to an apparatus that uses solar rays to convert water into gaseous hydrogen and oxygen. A specially constructed laminated sheet structure is immersed in an electrolyte so that solar energy impinging on the sheet surface generates an output voltage that electrolytically decomposes water into hydrogen and oxygen.
The various known prior art patents individually show isolated features used in my invention. My proposed system, as a single entity, is believed to be novel.